title: Population based nationwide study of hypospadias in Sweden, 1973 to 2009: incidence and risk factors.
abstract: OBJECTIVE
  We studied the incidence of hypospadias in Sweden during a 40-year period to determine if changes were associated with known risk factors.
  
  
  METHODS
  We analyzed prospective data from nationwide health care and demographic registers collected for all males (1,948,591 total) born in Sweden between 1973 and 2009. The incidence of hypospadias per 1,000 live-born boys was calculated as number of cases divided by total number of births yearly. The association between hypospadias and risk factors was estimated using logistic regression, expressed as odds ratios.
  
  
  RESULTS
  The nationwide incidence of boys diagnosed with hypospadias was approximately 4.5 per 1,000 live-born boys until 1990, increasing to 8 per 1,000 boys during the following decade. Mild and severe phenotypes comprised the increase. Boys born small for gestational age (OR 4.34), as a twin (OR 1.8), as a result of in vitro fertilization (OR 1.15), or with parents from Asia (OR 1.45) or continental Europe (OR 1.41) were at increased risk for hypospadias. Multivariate analyses revealed that changes in risk factors did not explain the increased incidence. However, a systematic change in the classification of the diagnosis in registers could not be ruled out.
  
  
  CONCLUSIONS
  This nationwide study demonstrates an increased incidence of hypospadias diagnoses in Sweden from 1990 to 1999 that is not attributable to previously known risk factors. The increase includes mild and severe phenotypes, suggesting that shifts in the diagnostic criteria are not the underlying cause.
authors.affiliation: Department of Women's and Children's Health, Pediatric Surgery Unit and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anna Skarin
authors.initials: AS
authors.lastname: Nordenvall
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Louise
authors.initials: L
authors.lastname: Frisén
authors.affiliation: Department of Molecular Medicine and Surgery, and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Pediatric Endocrinology, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Nordenström
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Department of Women's and Children's Health, Pediatric Surgery Unit and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Pediatric Surgery, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden. Electronic address: Agneta.Nordenskjold@ki.se.
authors.forename: Agneta
authors.initials: A
authors.lastname: Nordenskjöld
mesh_terms: D005307:Fertilization in Vitro; D005865:Gestational Age; D006801:Humans; D007021:Hypospadias / Q000453:epidemiology* / Q000208:ethnology; D015994:Incidence; D007231:Infant, Newborn; D008297:Male; D010641:Phenotype; D011446:Prospective Studies; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D014427:Twins
keywords: birth weight; cohort studies; ethnic groups; hypospadias; incidence